1. Field of the Invention
The present invention relates to an optical information recording medium, and in particular relates to an optical information recording medium, such as a Blu-ray disc, which includes an optical recording layer containing an organic dye and which has an increased recording density.
2. Description of the Related Art
As information recording media, optical information recording media, such as optical disks, are widely used. Examples of such optical information recording media include a medium, such as CD-R, in which a recording layer and a reflection layer are disposed in that order on a light-transmissive resin substrate with a thickness of 1.2 mm and a diameter of 120 mm or 80 mm. In recent years, a higher information recording density has been required. Under these circumstances, a method has been conceived in which the laser wavelength is decreased and an object lens having a high numerical aperture (NA) is used, and thus, optical information recording media, such as DVD+R and DVD−R, have been realized. DVD+R or DVD−R has a structure in which, in order to increase the permissible value of the angle of tilt of the disk due to a decrease in wavelength and an increase in NA, two light-transmissive resin substrates with a thickness of 0.6 mm are bonded to each other with a reflection layer and a recording layer provided therebetween.
Furthermore, in recent years, in order to record high-definition image data, a much higher information recording density has been required. Under these circumstances, an optical information recording medium has been proposed which, as in a Blu-ray disc (BD-R), has a structure in which a reflection layer and a recording layer are disposed on a surface of a resin substrate with a thickness of 1.1 mm, and a light-transmissive layer with a thickness of 0.1 mm is disposed so as to cover the surface provided with the reflection layer and the recording layer. Specifically, the optical information recording medium includes a light-reflective layer, a phase-change recording layer, and a light-transmissive layer with a thickness of about 0.1 mm disposed on a disk-shaped substrate having an outer diameter of 120 mm, an inner diameter of 15 mm, and a thickness of about 1.1 mm, and by performing irradiation of laser light with a wavelength of about 405 nm from an optical head with a numerical aperture of about 0.85, user information can be recorded in the recording layer.
Use of a recording layer containing a dye, instead of the phase-change recording layer, is also under study. Japanese Unexamined Patent Application Publication No. 2006-147135 discloses an optical information recording medium 110 which includes at least a dye recording layer 113 containing an organic dye and a light-transmissive layer 116 composed of a resin disposed on a substrate 111 (refer to FIGS. 3 and 4). In the optical information recording medium 110, an intermediate layer 114 is provided between the dye recording layer 113 and the light-transmissive layer 116 (or an adhesive layer 115), the intermediate layer 114 preventing mixing of the dye recording layer 113 and the light-transmissive layer 116 (or adhesive layer 115). The intermediate layer 114 is composed of a Ta-containing compound, a Nb-containing compound, or a compound oxide containing Ta and/or Nb. The intermediate layer 114 has a thickness of 1 to 80 nm.
The optical information recording medium 110 described above as the related art includes an intermediate layer 114 composed of an inorganic substance, such as a Ta-containing compound or a Nb-containing compound, disposed between the dye recording layer 113 and the light-transmissive layer 116. Since adhesion between the intermediate layer 114 and the light-transmissive layer 116 (or adhesive layer 115) is not good, delamination easily occurs at the interface between the intermediate layer 114 and the light-transmissive layer 116 (or adhesive layer 115). In particular, when a user drops by mistake the optical information recording medium 110 to the floor or the like, delamination easily occurs from an outer peripheral side 111d of the optical information recording medium 110 at the interface between the intermediate layer 114 and the light-transmissive layer 116 (or adhesive layer 115). The occurrence of delamination at the interface between the intermediate layer 114 and the light-transmissive layer 116 (or adhesive layer 115) results in degradation in quality in terms of appearance as well as degradation in environmental resistance (moisture resistance), etc., which is a problem.